PROJECT SUMMARY Taste buds are complex multicellular endorgans essential for detection of taste. The cells of a taste bud distinguish between the nutritious and the potentially toxic, and communicate this information to the taste nerves innervating them. Despite recent advances in understanding the molecular signaling underlying taste transduction, a complete understanding of cell-cell interactions and transmission of information to the peripheral nervous system is lacking. We propose to use a newly invented technology, serial blockface scanning EM, to generate a complete 3D picture of taste bud structure from both mice and humans in order to test whether taste information is transmitted along dedicated ?labeled lines? dedicated to an individual taste quality, or whether the brain receives a more complex signal from the taste buds. The novel EM technology will permit detailed 3D reconstruction of the taste bud connectome allowing for analysis of key features including: 1) whether individual nerve fibers make functional contact with more than one cell type in a bud, and 2) whether the glial-like Type I cells fully separate the other cell types or whether there is potential for functional interactions between receptor cells encoding the different taste qualities. This greater understanding of the detailed structure of taste buds will help investigators formulate data-based hypotheses regarding functional interactions between the different cellular elements and a more clear understanding of how taste information is transmitted from taste buds to brain.